Process for preparing thick and thin novelty yarns



United States Patent Ofiice of Delaware No Drawing. Filed .luly 5, 1963, Ser. No. 293,182 8 Claims. (Cl. 264-290) This invention relates to the production of filaments, yarns and the like having randomly spaced thick and thin sections providing varying surface designs and unique optical effects in the finished fabrics.

It is known that a textile yarn having abrupt changes in denier along its length is capable of producing a fabric possessing unique visual and tactile properties. To provide this type of yarn, the normal procedure utilized for cellulose acetate yarns, polyethylene terephthalate yarns and the like, is to pass the yarn around a heated driven roller in such a manner so that intermittent sections of the yarn are heated and thereafter applying a uniform drawing tension to the yarn. This method may provide a satisfactory thick and thin filament or yarn, but it is essential to utilize special expensive and complicated equipment to provide the desired product. For example, a special type roller having its surface indented with longitudinal channels which is a requirement to provide the intermittent heated sections of the yarn and at the same time a complicated method of supplying the yarn to the heated roller, such as a reciprocating bar, is an additional requirement. It is readily apparent that these additional requirements to prepare a thick and thin filament or yarn are complicated, expensive and can provide undesirable problems.

It is the over-all object of this invention to provide a simple and unique process for the production of the desirable randomly spaced thick and thin yarns made from polymethylene terephthalate polymers.

It has been discovered that polymethylene terephthalate yarn having randomly spaced thick and thin sections can be produced by drawing or stretching undrawn polymethylene terephthalate yarn or filaments from about 2.8 to about 3.5 times its original length at a temperature in the range from about 30 C. to its second order transition temperature, at drawing speeds in the range from about 1100 to about 1600 feet per minute. The unique feature of this process relates to the fact that under the abovedescribed conditions, a randomly spaced thick and thin yarn is provided without any further processing technique such as an isolated heated source to intermittently heat portions of the filaments or yarn and similar devices. Furthermore, utilizing the desired yarn product of the process to produce finished fabrics will provide highly desirable varying optical effects by a single dyeing operation. The fabrics thus produced with an eye appealing random surface design can be utilized in the production of dresses, drapes, upholstery, and the like.

The drawing or stretching operation of this invention can be carried out on undrawn polymethylene terephthalate filaments or yarns which have been allowed to cool and solidify. Any simple and suitable apparatus and process may be used for drawing. For instance, the yarn or filaments may be wound from one roller to another; the second roller rotating at a higher speed than the first roller so as to draw or stretch the yarn or filaments 2.8 to 3.5 times, preferably 3.0 to 3.5 times, its original length. It has been found that if the undrawn polymethylene terephthalate filaments or yarns are drawn below 2.8 times their original length under the conditions of the process of this invention, an undesirable product which is exceptionally poor in fiber physical properties will be obtained. On the other hand, if the undrawn filaments or yarn are stretched above 3.6 times its original length under the conditions of this process, a completely uniform fiber will be obtained destroying the desired properties of the thick and thin yarn product.

It is another critical feature of the: process of this invention to maintain a temperature of the yarn or filaments being drawn or stretched at or below the second order transition temperature of undrawn polyethylene terephthalate filaments or yarns; The term second order transition temperature as used herein, is defined in Fibres From Synthetic Polymers, Elsevier Publishing Company, 1953, at page 322. The second order transition temperature can vary depending on the nature of the polyethylene terephthalate product. For example, for non-crystalline undrawn polyethylene terephthalate the second order transition temperature is 69 C. and for crystalline undrawn polyethylene terephthalate the second order transition temperature is 81 C.

The birefringence of the undrawn polymethylene terephthalate of this process can range from about 0.0005 to 0.009, preferably in the range from about 0.007 to about 0.009. The birefringence or double refraction of a polymeric structure having a longitudinal axis is primarily dependent upon the orientation of the polymer molecules along the longitudinal axis and is a convenient measure of such orientation. The birefringence, which is also called the specific index of birefringence, may be measured by the retardation technique described in Fibres From Synthetic Polymers by R. Hill (Elsevier Publishing Company, New York, 1953), pages 266-8, using a polarizing microscope with rotatable stage together with a cap analyzer and quartz wedge. The birefringence is calculated by dividing the measured retardation by the measured thickness of the structure expressed in the same units as the retardation.

Utilizing conventional spinning conditions, the polymethylene terephthalate undrawn yarn produced contains a birefringence in the range from about 0.007 to about 0.009. Utilizing this conventional undrawn yarn, if temperatures of the filament or yarn exceed 70 C., the thick and thin characteristics of the resulting product can be destroyed. The minimum temperature of the yarn or filaments in drawing is determined by practical economic aspects. The preferred temperature of the filament or yarn for drawing ranges from about 30 C. to C. At the higher temperatures, heat can be supplied to the yarn prior to the drawing stage or it can be supplied by heating the drawing apparatus, such as the rollers, which may be utilized. Another method of supplying heat to the yarn of filament is by passing an undrawn material over a metal plate maintained at room temperature and the friction caused by intimate contact of the yarn with the metal plate can provide sufficient heat. The preferred temperature range of 30 C. to 69 C. of the filament yarn is highly desirable since these conditions permit the highest possible drawing speed and can, therefore, provide production economic advantages over the lower temperatures. It should be noted, of course, that if the undrawn yarn to be used in the process of this invention is crystalline in nature, temperatures of the yarn in excess of 69 C. can be tolerated and temperatures as high as 81 C. can be utilized; however, in any event, the second order transition temperature of the undrawn yarn cannot be exceeded to obtain the desired product of the process of this invention.

The drawing speeds which can be used range from about 1100 feet per minute to 1600 feet per minute, depending on the temperature of the polymethylene terephthalate yarn to be drawn. At the preferred drawing speeds of 1100 to 1500 feet per minute, considerable care must be used to avoid an increase of temperature above 69 C. of the yarn due to the friction of the contacting Patented Sept. 27, 1966 am with the apparatus. The term drawing speed 15 used herein is defined as the rate at which the final drawn product comes off the draw roll. For purposes )f convenience, the drawing speed is measured in feet ger minute.

It is essential for purposes of this invention that the :onditions used for the undrawn polymethylene tereph- ;halate yarns or filaments are utilized in the ranges described so as to provide the desired optimum product. The term yarn or filament as used herein can describe a single continuous filament or a group of continuous filaments designated as yarn, which is well known in the art. Under the conditions of the process of this invention, the weight of the undrawn yarn utilized should not exceed 10,000 denier, preferably less than 4,000 denier and more preferably less than 1,000 denier. The weight and size of the single continuous filament is determined by its practical usage in the textile art and can range from 0.5 denier or less upward to 50 denier per filament or more.

After the yarn has been drawn according to the conditions of the invention, the resulting product can be stabilized by subjecting said yarn to a heat treatment at temperatures in the range from about 100 C. to about 280 C., preferably in the range from about 200 C. to about 220 C., for a period of time suflicient to provide a relaxed yarn. The purpose of the heat treatment or relaxing step is to provide a yarn which will not shrink in excess of 10 percent, preferably less than 5 percent, of the original length; but the period of time of heat treatment cannot extend beyond that period which would decompose the yarn product. The length of time of heat treatment is proportional to the temperature used, i.e. at lower temperatures a longer heat treatment can be tolerated, but at higher temperatures a shorter period of time of exposure is essential. For example, the heat treatment of the yarn product at 100 C. can tolerate a dwell time or exposure time for as long as 15 minutes and longer, if desired, without significant detrimental effects; however, at heat treatment temperatures of 280 C., the dwell time should not exceed .01 second. The heat treatment can be conducted by steaming, infrared heat, dielectric heat, passing the yarn through hot inert fluids, or the like.

The fiber-forming polymethylene terephthalate polymer can be prepared by the conventional polycondensation process of an alkylene glycol containing from 2 to carbon atoms and terephthalic acid or an ester-forming derivative thereof and subsequently polymerizing the resulting product. During the preparation of the polyester polymer, minor amounts of known modifying material, if desired, may be added, e.g. various glycols, various dicarboxylic acids and the like. These modifiers may be added as one of the initial reactants during the polymerization process, but the modifying material may also be polymerized separately and melt blended with the polymethylene terephthalate polymer, if desired. The total amount of modifier in the final polymer material should not exceed mol percent. The preferred polymethylene terephthalate polymer used to prepare the undrawn yarns in the process of this invention is polyethylene terephthalate which can be produced according to known procedures similar to the conditions described in U.S. Patent 2,465,319, to Whinfield and Dickson. The range of intrinsic viscosity of the polymer produced under these conditions can range from about 0.2 to about 1.0 deciliter per .gram with a preferred range from about 0.4 to about 0.8 deciliter per gram as measured in orthochlorophenol.

In preparing the undrawn polymethylene terephthalate yarns for use herein, the polymer prepared by a conventional polymerization process can be cooled, if desired, broken into chips and dried. The chips are then melted and pumped, in a completely standard way, by means of a metering pump of the type commonly used in the manufacture of synthetic fibers through a filter pack and spinneret orifices into room temperature air. The extruded filaments cool and solidify by passage through the air and are then ready to be subjected to the process of this invention.

The following examples will serve to illustrate the process of the invention without limiting the same:

Example 1 An ethylene glycol terephthalate polymer having an I.V. in the range from 0.50 to 0.70 deciliter per gram (measured in ortho-chlorophenol) and having a birefringence of 0.0082 is melt spun and collected as 270 denier-36 filament yarn. This yarn is passed over a metal plate with contact and passed around suitable rolls maintained at room temperature (21 C.) to impart a draw of 3.5 times its original length. The draw speed of the second roll is 1500 feet per minute and the yarn product is collected on a bobbin. The temperature of the yarn during the drawing does not exceed 65 C. The resultant yarn had the following properties:

Mean denier/ number of filaments 78/ 36 Twist, mean turns per inch 0 Shrinkage, percent at C 21 Denier variability (Uster), percent 18 Tenacity, grams per denier 4.2 Elongation, percent 98 Luster Semi-dull Spacing of thick portions (slubs) Random Number of thick portions (slubs) per 100 yards Length of .slubs, range in inches 0,5-10 Typical maximum denier 270 Broken filaments None Loopy filaments None The yarn product is woven into a fabric which corresponds to a smooth shantung or smooth douppioni effect. In a single dyeing operation, the thick portions of the fabric provide a deeper shade than the thin portions, thereby providing an eye appealing random surface design.

Example 2 An ethylene glycol terephthalate polymer having an LV. in the range from 0.50 to 0.70 deciliter per gram (measured in ortho-chlorophenol) and having a birefringence of 8.2 10 is melt spun and collected as 270 denier-60 filament yarn. The yarn is passed around suitable rolls maintained at 65 C. to impart a draw of 3.0 times its original length. The draw speed of the second roll is 1500 feet per minute. The temperature of the yarn does not exceed 69 C. during the drawing procedure. The yarn product is passed through a hot air oven at a temperature of 210 C. for a dwell time of 0.1 second. The yarn product is collected on a bobbin. The physical properties of the yarn and finished fabric are similar to the products as described in Example 1.

Example 3 The following example illustrates the control conditions of this process. Under the conditions similar to those of Example 2, the ethylene glycol terephthalate yarn is drawn over rolls maintained at 70 C. to impart a draw of 3.5 times its original length. The yarn temperature on drawing is always maintained at 70 C., or above. A similarly uniform fiber is obtained with only small amounts of thick portions of yarn present in a uniform distribution. The finished fabric of this yarn does not provide the eye appealing surface design as is present in the fabrics made from the yarn by the proces of the present invention. The result in this example is undesirable and, on dyeing, provides a condition described as dye specks.

In a similar manner as described above, except that the drawing ratio is 2.7, undesirable extensive lengths of fixed sections of yarns are obtained with a small uniform distribution of thin sections. The physical properties of this yarn are exceptionally poor for producing a finished fabric.

Example 4 An ethylene glycol terephthalate polymer having an I.V. in the range from 0.40 to 0.80 deciliter per gram (measured in ortho-chlorophenol) and having a birefringence of 8.2 is melt spun and collected as 270 denier-60 filament yarn. At drawing, a 1.3 percent emulsion containing a mixture of mineral oil, ethyl stearate and an emulsifying surface active agent is applied to the yarn. The yarn is then passed around suitable rolls maintained at 65 C. to impart a draw of 3.5 times its original length. The draw speed of the second roll is 1200 feet per minute and the yarn product is collected on a bobbin. The temperature of the yarn does not exceed 69 C. during the drawing procedure. The physical properties of the yarn and finished fabric are similar to the products as described in Example 1,

It is undestood that the foregoing description is merely illustrative of preferred embodiments of the invention of which many variations may be made by those skilled in the art within the scope of the following claims without departing from the spirit thereof.

What is claimed is:

1. A process for producing polymethylene terephthalate yarn having randomly spaced thick and thin sections which comprises drawing undrawn polymethylene terephthalate yarn having a birefringence from about 0.0005 to about 0.009 from about 2.8 to about 3.5 times its original length, at a temperature of said undrawn yarn in the range from about 30 C. to the second order transition temperature of said undrawn yarn, at drawing speeds in the range from about 1100 to about 1600 feet per minute.

2. The process of claim 1 wherein the yarn product is heat treated at a temperature in the range from about 100 C. to about 280 C. for a period of time sufficient to provide a relaxed yarn.

3. A process for producing polymethylene terephthalate yarn having randomly spaced thick and thin sections which comprises drawing undrawn polymethylene terephthalate yarn having a birefringence from about 0.007 to about 0.009 from about 3.0 to about 3.5 times its original length, at a temperature of said yarn in the range from about 30 C, to about C., at drawing speeds in the range from about 1100 to about 1500 feet per minute.

4. The process of claim 3 wherein the yarn product is heat treated at a temperature in the range from about 200 C. to about 220 C. for a period of time sufficient to provide a relaxed yarn.

5. A process for producing polyethylene terephthalate yarn having randomly spaced thick and thin sections which comprises drawing undrawn polyethylene terephthalate yarn having a birefringence from about 0.0005 to about 0.009 from about 2.8 to about 3.5 times its original length, at a temperature of said undrawn yarn in the range from about 30 C. to the second order transition temperature of said undrawn yarn, at drawing speeds in the range from about 1100 to about 1600 feet per minute.

6. The process of claim 5 wherein the yarn product is heat treated at a temperature in the range from about C. to about 280 C. for a period of time sufiicient to provide a relaxed yarn.

7. A process for producing polyethylene terephthalate yarn having randomly spaced thick and thin sections which comprises drawing undrawn polyethylene terephthalate yarn having a birefringence from about 0.007 to about 0.009 from about 3.0 to about 3.5 times its original length, at a temperature of said yarn in the range from about 30 C. to about 65 C., at drawing speeds in the range from about 1100 to about 1500 feet per minute.

8. The process of claim 7 wherein the yarn product is heat treated at a temperature in the range from about 200 C. to about 220 C. for a period of time sufficient to provide a relaxed yarn.

References Cited by the Examiner UNITED STATES PATENTS 2/1956 Calton 264290 1/ 1964 Guandique et a1 161170 

1. A PROCESS FOR PRODUCING POLYMETHYLENE TEREPHTHALATE YARN HAVING RANDOMLY SPACED THICK AND THIN SECTIONS WHICH COMPRISES DRAWING UNDRAWING UNDRAWN POLYMETHYLENE TEREPHTHALATE YARN HAVING A BIREFRINGENCE FROM ABOUT 0.0005 TO ABOUT 0.009 FROM ABOUT 2.8 TO ABOUT 3.5 TIMES ITS ORGANIAL LENGTH, AT A TEMPERATURE OF SAID UNDRAWN YARN IN THE RANGE FROM ABOUT 30*C. TO THE SECOND ORDER TRANSITION TEMPERATURE OF SAID UNDRAWN YARN, AT DRAWING SPEEDS IN THE RANGE FROM ABOUT 1100 TO ABOUT 1600 FEET 